1. Field of the Invention
The present invention generally relates to a thermal control method and device, and in particular to a method and device to regulate the rotational speed of a fan cooler by thermal control, whereby the fan cooler can be actively adjusted to work at an appropriate speed to maintain the inner temperature of an apparatus within a selected moderate temperature range. Thereby, a balance between temperature reduction and power consumption can be achieved.
2. Description of Related Art
Heat is always generated while ordinary electronic equipment is turned on. For example, a personal computer having a high-speed microprocessor will generate a large amount of heat. Various devices for reducing temperature have been developed to avoid the negative effects of excess heat on electronic devices, such as a shortening of component lifetime and malfunction.
There are two general types devices for dissipating heat. One uses a mechanical structure, such as a radiator plate or a conduction heat plate, to perform heat dissipation. The refrigerant efficiency depends on the contact area between the heat generating component, such as the heating microprocessor, and a radiator or a heat conduction plate. Generally speaking, the refrigerant efficiency is higher when the contact area is larger, and vise versa. However, the application of such a mechanical structure for heat dissipation in portable electronic devices (for example, notebook computers) is restricted by the limited volume available to each component equipped therein because a large contact area is not feasible. When the operational speed of the portable electronic device becomes very fast, a limited contact area may be too small to achieve the purpose of heat dissipation.
The other type of heat dissipating device uses a fan cooler or a cooling installation to dissipate heat. Fan coolers are usually applied in portable electronic devices which need high refrigerant efficiency due to their smaller volume.
Most fan coolers used in portable electronic devices are powered by a constant voltage in either a turned on or off state, and whether or not the fan cooler starts to dissipate heat is determined by a control mechanism of the portable electronic device. But there are several disadvantages in the foregoing fan of the prior art. First, unlike the radiator plate, the fan cooler must be powered to rotate as fast as possible in order to effect heat dissipation, so a portion of the limited electric power stored in the portable electronic device will be consumed. This negatively impacts the ability of portable electronic devices to strictly control power consumption. In addition, fan coolers rotating at the full speed will make a significantly loud noise, which is also a problem that needs to be resolved.